Experimental study of electronic expansion valve opening on the performance of electric vehicle heat pump system at different compressor speeds

Abstract

The good matching of the electronic expansion valve (EXV) opening and compressor speed in an electric vehicle heat pump air conditioning system is significant for improving the whole system performance. The matching of EXV opening and compressor speed and its effect on system performance was experimentally investigated and analyzed. The results showed that at various compressor speeds, the condensing pressure increased and the evaporating pressure decreased to a small extent with the decrease of EXV opening, thus increasing the pressure ratio. The condensing pressure had a jump phenomenon at a specific EXV opening, and the corresponding jump opening was different at each compressor speed. The COP reached the optimal values of 2.4, 2.6, and 2.1 at the EXV opening of 110, 100, 90 steps, respectively, due to the synergistic effect between compressor speed and EXV opening. Moreover, it was found that the changing trend of COP was consistent with that of condenser outlet temperature. The compressor speed and EXV opening had a more significant impact on condensing pressure than evaporating pressure. The influence of compressor speed on each performance parameter was greater than that of EXV opening, while the EXV opening significantly influenced the subcooling degree. Under different compressor speed conditions, changing the single adjustment step of EXV according to the influence of EXV on each parameter can realize the rapid and accurate control of the heat pump system performance, which can provide a reference for the formulation of relevant control strategies and the reduction of the system energy consumption.